Tuneable resonators are used in many electronics applications, such as, for example, filters and Voltage Controlled Oscillators.
At present, a common kind of tuneable resonator used is the so called LC-resonator, which usually includes a semiconductor varactor. A drawback with LC-resonators is that their Q-factor is usually limited by the losses in their inductor coils.
Another kind of resonator which is also commonly used at present is the so called Thin Film Bulk Acoustic Resonator (TFBAR), which offers substantially higher Q-factors. However, TFBAR:s usually utilize piezoelectric material, which leads to the TFBAR:s not being tuneable, e.g. because the piezoelectric materials do not have DC voltage dependent acoustic parameters.